Steve - "Yeah, so?"
Bob - "That's pretty darn Metric of you."
Comparing the Metric and Secondary (Or standard as some call it) measurement systems in America, we find that the majority of people are more familiar with Secondary, and as such 'Metric' is awkward, different, bad, or crazy. In this sense, 'Metric' can be used to describe the attitude or actions of a person, or something else that has happened that was unintended and harmful or unwanted.
Paul: "Yea, they suck! Listen to some good music like Green Day, John Mayer, or Linkin Park!"
Randy then proceeds to push Paul's lifeless body into the Hudson.
Probably drawn from the idea that the metric system is "better" than other systems.
Lil Wayne: Yo dawggg, that shit was metric AF.
2. An adjective that describes something as making more sense, better, and/or more awesome than any other possibility.